Industrial manipulator hoist



May 16, 1961 M. R. NlELsEN ErAL INDUSTRIAL MANIPULATOR Hors':

2 Sheets-Sheet 1 Filed 001,. 18, 1956 and May 16, 1951 M. R. NIELSEN l-:TAL 2,984,376

INDUSTRIAL MANIPULATOR HoIsT Filed Oct. 18, 1956 2 Sheets-Sheet 2 INDUSTRIAL MANIPULATOR HOIST Milton R. Nielsen, Lombard, and Richard A. Slouka, Can,

` pentersville, Ill., assgnors to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Filed Oct. 18, 1956, Ser. No. 616,638 Claims. (Cl. 214-658) Our invention relates to hoists and more particularly hoists which are hydraulically operated.`

It is an object of our invention to provide an improved hoist of this type comprising a stationary and a movable part, with one of the parts having a cylindrical chamber therein and another of the parts constituting a piston slidable in the cylindrical chamber. It is contemplated that the hoist shall include a source of Huid pressure connectible with the cylindrical chamber for moving the piston within the cylindrical chamber for raising and lowering workpieces carried by the movable part.

It is another object of :the invention to provide in a hoist of this type a source of fluid pressure comprising a motor driven pump supplying iiuid to an accumulator having air therein for maintaining the iluid under pressure so that the movable part of the hoist may be moved with respect to the .fixed part even though the motor is inoperative at the time.

It is another object of the invention to provide a pair of jaws on the movable part of the hoist, one of which is moved by means of a piston connectible with the source of fluid pressure, so that a workpiece may be grasped between the jaws due to force derived from the source of tlnid pressure.

The movable part of the hoist preferably constitutes the piston above-mentioned, and it is another object of the invention to provide a relatively large cross-section fluid chamber above the piston and a relatively small crosssection fluid chamber below the piston within the cylindrical chamber, so that the source of fluid pressure may be permanently connected to thesmall cross-section iluid chamber, and the piston may be raised and lowered in the cylindrical chamber for raising and lowering a workpiece by connecting the large cross-section fluid chamber with the source of uid pressure or by draining the large cross-` section fluid chamber. j

It is another object of the invention to provide a control handle carried by the movable part of the hydraulic hoist which so controls fluid pressure application to the piston so that the movable part of the hoist moves upwardly when an upward force is put on the handle and moves downwardly when a downward force is put on the handle.

It is contemplated that the handle shall control a valve hydraulically connected with the cylindrical chamber for this purpose, with the valve being held in a neutral position corresponding to a stationary condition of the piston by spring mechanism, so that the velocity of travel of the movable part of the hoist increases with the force that is put on the handle tending to move the valve against the spring mechanism.

It is also an object of the invention to provide `another valvecontrolled by a button carried by .the control handle which controls the application of iluid pressure to a piston for moving a movable jaw, so that the movement of the jaw may be easily controlled along with movement of the movable part of the hoist.

It is another object of the invention to provide a motor driven pump and an accumulator as above-mentioned to act as a source of fluid pressure for the piston of the hoist and also for the piston moving the movable jaw, with the iluid pressure source including a check Valve workpiece between them.

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which closes when the source of fluid pressure fails. The check valve thus maintains a pressure on the piston of the hoist holding the movable part of the hoist in a raised position and also maintains a pressure on. the piston for the jaw, for likewise holding the jaws to firmly grasp a 'I'he invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will be apparent from the following description of preferred forms of the invention, illustrated with reference to the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view of a hydraulic hoist embodying the principles of the invention;

Figure 2 is a sectional view on an enlarged scale taken on line 2 2 of Figure 1;

Figure 3 is a side view of certain valve mechanism taken on line 3-3 of Figure 2 in the direction indicated; and

Figure 4 is a side elevational View of the lowermost part of the hoist showing a hook substituted for one of the jaws of the hoist.

' Like characters of reference designate like parts in the several views.

Referring now to the drawings, the illustrated hoist comprising, in general, an upper support cylinder 10, a lower support piston 11, a pump 12 for providing fluid under pressure, an electric motor 13 for driving the pump, a fluid accumulator 14, a reservoir 15 for a uid such as oil, a workpiece gripping jaw assembly 16, and a valve assembly 17 for controlling movement of the lower support piston 11 and for controlling relative movement between the jaws of the assembly 16.

The iuid reservoir 15 may comprise any suitable closed sheet metal container 18 having an eXit port 19 and a return port 20. The container is iilled with a suitable iluid such as oil.

The pump 12 may be of any suitable construction and has an inlet port 21 and an outletport 22. The pump is driven by the electric motor 13 which may be of any suitable conventional construction. The pump inlet port 21 is connected by means of a conduit 23 with the exit port 19 in the container A18. A check valve 24 is connected to the pump outlet port 22 and may comprise a ball 25 urged by means of a spring 26.0nto a seat 27.

The pump outlet port 22 of the pump 12 is connected through the check valve 24 and a conduit 28 with a port 29 of the fluid accumulator 14. The fluid accumulator 14 may comprise simply a closed metal vessel 30 which is partially lilled with a body of uid 31, with a volume of air 32 being disposed above the body of uid 31.

The electric motor 13 is controlled in its operation by a pressure switch assembly 33. The pressure switch assembly 33 is connected by means of a conduit 34 with the accumulator port 29 and may comprise a diaphragm 35 which is subject to the pressure of the iluid .in the fluid accumulator 14. The motor 13 is provided with two electrical leads 36 and 37 for supplying electric power to the motor, and a switch 38 is disposed in one of the leads 36. The switch 38 comprises a iixed contact 39 and a movable contact 40, and a pin 41 carried by the diaphragm 35 is adapted to actuate the movable contact 40 and open the switch 38.

A conduit 42 connected with the port 29 of the iluid accumulator 14 constitutes a source of uid pressure for the lower support piston 1'1, and a check valve 43 is disposed in the conduit 42. The check valve 43 may be of any suitable conventional construction and, as illustrated, comprises a ball 44 yieldably held on a seat 45 by means of a spring 46. l

The uid accumulator 14, the pump 12, the associated upper end. The upper support cylinder is provided onV its lower end with an inwardly extending lip 49, and a tube 50 extends downwardly through the cylinder at the center thereof. The tube50 is connected by means of a conduit 51 with the return port 20 of the iiuid reservoir 15. The upper support cylinder 10 is provided with a port 52 adjacent the lip 49 which is connected to the conduit 42 constituting the source of fluid pressure.

The lower support piston 11 comp-rises an enlarged cylindrical piston head 53, and a tubular, relatively small diameter cylindrical depending piston portion 54. A seal 55 is provided between the enlarged cylindrical piston head 53 and the inner surface of the upper support cylinder 10, and a seal 56 is provided |between the enlarged cylindrical piston head 53 and the tube 50. A seal 57 is provided between the lip portion 49 of the upper support cylinder 10 and the exterior surfaceof the cylindrical depending piston portion 54. The seals function to prevent leakage between the lower support piston 11 and the upper support cylinder 10 and tube 50. l

The Vupper support cylinder 10 forms a liuid chamber 58 above the enlarged cylindrical vpiston head 53 of the lower support piston 11, and the lower support piston 11 provides a fluid chamber 59 between the enlarged cylindrical head piston 53, and the lip 49 of the upper support cylinder 10. The cylindrical depending piston portion 54 provides a iiuid chamber 60 within itself.

Conduits 61 `and 62 extend through the lower support piston 11. The conduit is connected to a port `63 provided in the enlarged cylindrical piston head 53 in communication with the fluid chamber 58, and the conduit 62 is connected to a portu 64 which is in communication with the fluid chamber 59. 4

The valve assembly 17 comprises a casing 65v fixed to the lower end oct theV lower support piston 11 and a pair of valves 66 and 67. The jaw assembly 16 comprises a fixed ja'w 68 and a movable jaw 69. The valve assembly includes also a piston 70 for moving the movable jaw 69.

The valve 66 is for the purpose of controlling upward and downward movement of the lower support piston 11 within the upper support cylinder 10. The valve 66 cornprises a valve piston 71 having lands 72, 73 and 74 formed thereon.

in. The ports 76, 77 and 78 are respectively in communication with the iiuid chamber 60 in the lower support piston 11, the conduit 61 and the conduit 62.

The valve piston 71 is yieldably held in its illustrated neutral position by means of centering springs 79 and 80. The spring 79 is disposed between an end portion of the casing 65 and a washer 81 which rests on an end of the tubular valve part 75. The spring 80 is disposed between an end portion of ,the casing 65 and a washer 82 which rests on the other end of the tubular valvepart 75.

A handle 83 is utilized for controlling the valve 66. The handle is swingablyv journalled with respect to the casing 65 by means of studs 84 and 85. The studs 84 and 85 are fixed with respect to the handle 83, and the stud 84 carries a pin 86 eccentrically disposed with respect to the center of the stud 84. The vpin 86 fits within a slot 87 formed in the valve piston 71.

The valve 67 which is for the purpose of controlling the movement of the movable jaw 69, comprises a valve piston 88 having lands 89 and 90. The valve piston 88` is slidably disposed in a Vtubular part 91 having ports 92,Y

93 and 94 therein. The ports 92, 93 and 94 are respectively connected with the iiuid cavity 60 in the lower supportpiston 11,'the conduit 61, and the conduit 62.

The valve pistonv 71 is-slidably disposed in a` tubular housing part 75 having ports 76, 77 and 78 there-l The valve piston 88 is yieldably held in its illustrated position by means of a spring 95 which is disposed between an end portion of the casing 65 and a washer 96 which rests on an end of the ,tubular valve part 91.

The valve piston 88. is controlled by means of a jaw release button 97 which is formed onV theend of a bell crank lever 98 pivotally mounted by means of a pin 99 ina slot 100 formed in the handle'83. The inner end of the lever 98 is adapted to make contact with the valve piston 88 andV to move the valve piston 88 to the left as seen in the drawing. A spring 101 is provided between an inner surface of the handle 83 and a pin 102. fixed to the leverl 98 for yieldably holding the lever 98 in contact with the piston 88. A button guard 103 is prefer-I ably disposed around the jaw release button 97 for preventing inadvertent actuation of the jaw release button The piston 70 comprises an enlarged piston head 104 ton stem portion 106 of reduced diameter extending through an aperture formed by an inwardly extending` lip portion 107. A fluid chamber 108 is provided by the lip portion 107 and the enlarged piston head 104, and this fiuid chamber 108 is connected by passage 109 with the port 93 of the valve 67 The jaw 69 is fixed on the end of the piston stem portion 106, anda spring 110 is provided between the jaw jaws 68 and 69.

69 and the lip portion 107. The other jaw 68 is fixed, as

by means of a stud 111, to the casing 65. Each of the.

jaws 68 and 69 is provided with a recessed portion 112 for better holding of certain work pieces between the to move the jaws 69 and 68 apart, and after a,work.

piece is positioned between the jaws, the button is released, causing the movable jaw k69 to move toward the Y fixed jaw 68 and grasp the workpiece.

The handle 83 is utilized for the purpose of moving the jaws 68 and 69 upwardly by a movement of the lower support piston 11 in the upper support cylinder 10, and the handle is also utilized for causing the lower support 'i piston 11 and jaws 68 and 69' to descend. The movement of the jaw 69 is obtained by means of the valve 67 while the upward and downward movement of the jaws is obta-ined by virtue of the functioning of the valve 66; both of the valves being connected with a source of fluid p-ressure provided by the pump 12- The pump 12 is driven by the motor 13 and draws fluid from the fluid reservoir 15 through the port 19, the conduit 23 and the pump inlet port 21. Fluid Ais discharged from the pump 12 through the check valve 24 and conduit 28, to the port 29 of the'fiuid accumulator 14 and to the conduit 42 through the check valve 43; the conduit 42 acting as a iiuid pressure source with respect to the lower support piston 11and the valvesv 66 and 67.

The fluid discharged Iby the pump 12 flows into the iiuid n accumulator through the port 29 and compresses the body of air 32 lin the fluid accumulator until a predetermined pressure of the fluid is reached. This fiuid under pressure is applied to the diaphragm 35 of the pres-V sure switch assembly 33 through the conduit 34; and the fiuid under pressure moves the pin 41 which is attached to the 'diaphragm 35, to the right, as seen in the drawings, so as to move by contact, the `contact 40 away from the contact 39 when this predetermined fiuid pressure is reached. At that time the switch 38 opens the lead 36 l and causes the motor 13 to cease functioning. The body of air 32 under pressure vin the iuid accumulator at this time maintains the fiuid in the conduits 34' and 42- approximately at this pressure, `even though some of it is utilized for moving the lower support piston 1-1 as will hereinafter beA explained. When usage of the uid from the uid accumulator 14 operating the hoist drops the fluid pressure below a certain predetermined value, the switch 38 will 'close rand again energize the motor 13 to drive the pump 12and cause `the uid pressure to be again raised to the predetermined pressure at which the switch 38 is opened. t l

The check valve '24 operates to prevent a back ilow of uid from the fluid accumulator 14 through the pump 12 and conduit 23 into the fluid reservoir 15 when the motor 13 is inoperative due to opening of the switch 38. A loss of pressure in the iiuid accumulator 14 is thus avoided. Y

When the free end of the handle 83 is moved upwardly, swinging the handle 83 4about the journals of the studs 84 and '85,the valve piston 71 is moved `to the right as seen in the` drawings. This `movement of the valve piston 71 is caused Aby the eccentrically disposed pin `86 acting in the slot 87 formed inthe valve piston 71. 'I 'his movement of the valvepiston 71 is1 against the actionofV the spring 80; the end of theland 74 acting through the washer 82 against the spring 80.

As has been explained, the conduit 42 acts as a source of fluid pressure, and this fluid pressure flows through the port 52 into the uid chamber 59. Fluid in this fluid chamber 59 tends, as will be understood, to move the lower support piston 11 and particularly its enlarged cylindrical piston head 53 upwardly in the upper support cylinder 10, and such movement will occur, assuming that there is no fluid pressure in the upper support cylinder above the enlarged cylindrical piston head 53 preventing such upward movement. Fluid pressure also flows from the iiuid chamber `59 through the port 64 and conduit 62 to the port 78.

The valve piston 71 when so moved to the right contains the fluid pressure supplied to the port 78 between the lands 73 and 74; however, the valve piston 71 when so moved connectsthe ports 76 and 77 together. The port 77 is connected through the conduit 61 and port 63 with the uid chamber 58 above the lower support piston 1 1,` and fluid above the lower support piston 11 may thus flow through the port ,63, the conduit 61, the port 77, the groove between the lands 72 and 73, the port 76, the lluid chamber 60, the conduit 50, the conduit 51 and the port 20 back into the fluid reservoir 15. This release ofuid `in the fluid chamber 58 allows the uid under pressure `inthe fluid chamber 59 to move the lower support piston 1v1 upwardly, and such movement continues until the handle 83 is moved back into its neutral position, which causes the valve piston 71 to move into its neutral position as illustrated, which blocks the port 77 with respect to the port 76 as well as with respect to the port 78.

It should be noted that the jaws 69 and 68 carried by the casing 65 andthe lower support piston 1,1 move upwardly when the pressure on the handle 83 is in the upward direction and that such upward movement continues as long as the operator puts pressure on the handle 83 in the upward direction. The upward motion of the jaws 68 and 69 follow along with the vertical motions of the operators hand on the handle 83, and it will be noted that increasing the pressure on the handle 83 in the upward direction will move the Valve piston 71 farther to the right againstthe yieldable spring 80 to cause a correspondingly rapid movement of the lower support piston 1 and jaws 68 and 69.l

l The lower support piston 11, and jaws 68 -and 69 may be lowered by putting a downward pressure on the handle 83. The handle 83 when swung downwardly moves the valve piston 71 to the left as seen in the drawing by means of the pin 86 and slot 87. The valve piston 71 when so moved `contains and isolates the port 76 connected with the fluid chamber 60, and the groove between the lands 73 and 74 connects the ports 77 and 78. The

port ;78 being connected'with the fluid chamber 59 containing uid under pressure, by means of the port 64 and the conduit 62, supplies pressure through the groove between the lands73l and 74 to the port 77 which isconnected through the conduit 61 and portl `63 with the fluid chamber 58 above the enlarged cylindrical piston `'head 53. Fluid under pressure is thusV supplied to the chamber 58, and this fluid pressure moves the enlarged cylindrical piston head 53 and the remainder of the lowerf4 neutral position, the port 77 connected with the fluid chamber 58 is again blocked so that additional uid isV not supplied to the fluid chamber 58, and the lower support piston 11 and the jaws 68 and 69 cease movement. In the case of a raise of the lower support piston 11 and the jaws 69 and 68, the `amount of pressure that vis put on the handle 83 in the upward direction determinesthe, velocity of the upward movement of the lower support` piston 11 yand the jaws 68 and 69, and likewise in the case of a downward movement. From this it is appar-A ent that the handle 83 follows the movement of the jaws 68 and 69.

The `movement of the;V movable jaw 69 may be controlled with respect to the stationary jaw 68 by means of the jaw release button 97. When the jaw release button 97 is pushed inwardly with respect to the handle 83,`

it functions to so move the valve 67 that the jaw 69 moves away from the jaw 68. This movement of the jaw release button 97 causes a swinging movement of the bell crank lever 98 about its pivot 99 against the action of the spring so as to move the valve piston 88 to the left. The valveV piston 88 when so moved closes port 94 by means of land 90 thus shutting off fluid under pressure in conduit 62, with which port 94 is connected, and connects the port 92 with the port 93 by means of the groove between the lands 89 and 90. Theuid chamber 10'8 between the enlarged piston portion 104 and the lip 107 is thus drained, the uid flowing from the uid chamber 108 through the passage 109, the port 93, the groove between the lands 89 and 90, the port 92, the fluid chamber 60, the conduit 50, the conduit `51 and the return port 20 back into the Huid reservoir 15. The spring 110 is then active to move the jaw `6,9 away from the jaw 68.

The jaws 69 and `68 may then be lowered by down-` ward pressure on the handle 83 as above described so that` duit 62 containing uid under pressure, anduid under pressure thus ows through the port 94, the grooves between the lands 89 and 90, the passage 109 Ito the uid chamber 108. The iluid under pressure in the fluid chamber 108 moves the piston 70 to the right as seen in the drawing against the action of the Aspring 110 so as `to move the movable jaw 69 towards the stationary jaw 68 and grasp the workpiece between the jaws, preferably utilizing the recessed portions 112 of the jaws to hold the workpiece from slipping downwardly under the action of gravity.

With the workpiece being` gripped between the jaws 69 and 68, the yworkpiece may be raised by putting an upward pressure on the end of the handle 83 as has been previously described.

It should also be notedthat the workpiece, together` with the'lower support piston 11 may be rotated with respect to the'v upper support cylinder 10 and the rest of the hoist :simply by putting a manual rotating force on the handle 83 or on the workpiece. The enlarged cylindricalpiston head 53 simply rotates in the upper support cylinder 10, and the fluid under pressure in the chamber 5,9, `by such s winging movement; maintaining the lower support piston 11, the jaws 69 and 68 and the workpiece within the jaws at substantially the same height. Thus, if the workpiece happens to be a shaft, for example, the shaftV can be picked up by means of :the hoist and then can 'be turned so asv to face in a completely different direction so that the shaft may for example be inserted into the chuck of a lathe. Also, because the hoist is swngably attached to a support the control handle 18 may be utilized to manually swing the hoist laterally to further facilitate the handling of a workpiece.

The check valve 43 functions as a safety device in the event of sudden loss of fluid pressure in the accumulator; as for example if the accumulator should suddenly dev elop a leak.V In this case, the check valve 43 closes by virtueof the fluid pressure built up in the fluid chamber 59 and the conduit 42, which forces the ball 44 against the seat'=45, and thus fluid pressure is maintained in the conduitV 42 andin they fluid chamber 59. Hence fluid underl pressure cannot escape from the fluid chamber 59 and allow the lower support piston 11, the jaws 68 and 69, and the workpiece carried by the lower support piston 11, to drop suddenly. It should be noted that the fluid remaining under pressure in the fluid chamber 59 remains under similar pressure in the fluid chamber 108 for vholding the workpiece gripped between the jaws 69 and 68,` since the fluid chamber 108 is connected through the passage 109, of the conduit 62 in the port 94 with the fluid chamber 59.

The hook 113 which is somewhat longer than the jaw 68maybe substituted for the jaw 68. In this case the jaw 69 still is movable due to the functioning of the jaw release button 97, but the jaw 69 has no particular function, inasmuch as it is contemplated that the workpiece may be hung onto the hook 113 to be raised and lowered as'jdesired under the control of the handle 83.

`Our improved hoist represents a very simple form of a material handling device. The handle83 being carried bythe valve casing 65 which is fixed to the lower support piston 11,controls the upward and downward movement of the lower support piston 11 by corresponding upward and downward pressure on the handle. A strong pressure on the handle 83 causes relative rapid movement of therlower support piston 11 and jaws 68 and 69 in the same direction as the force impressed on the handle, so that the jaws automatically follow the vertical motions ofthe operators hand. The hoist advantageously has a powered gripping device; namely, the jaw assembly 16, whichV is controlled by the jaw release button 97, conveniently mounted on the control handle 83.

Advantageously, the fluid chamber 59 is always supplied by fluid under pressure, and the upward and downward movements of the lower support piston 11 and the jaws `69 and 68 are obtained by either supplying more fluid under pressure to the fluid chamber 58 or yby draining the fluid chamber 58. Since the fluid chamber 58 has a larger cross sectional `area than the fluid chamber 59, supplying fluid under the same pressure in both chambers will result in a lowering of the lower support piston 11 and the jaws `69 and 68. The supply of fluid under pressure to or the draining of fluid under pressure from the fluid chamber 58 by means of the handle operated valve 66 due to movement of the handle 83 either upwardly or downwardly controls thellow of fluid such that the lower support piston 11 moves in the same direction and at a velocity corresponding to that of the operators hand.

The hoist is relatively compact. The control Valves 66 and 67 are contained in a casing 65 carried by the lower support piston 11 and located adjacent tolthevcontrol handle 83. vThe fluid passages 61 and 62 are advantageously located within the lower support pistoni 11 and thus are not subject to damage as if theywere externally! located. Furthermore, the fluid reservoir l15 andthe fluid pressure supply mechanism are all located at thetop of the hoist out of the way, and preferably all -are enclosed within the housing 47.

The check valves 43 and 24 advantageously assure that` even though there may be a failure of the fluid accumulator 14 or of the motor 13 or pump 12, thelower support piston 11 together with any workpiece carried by the jaws 69 and 68 cannot suddenly drop, perhaps caus- As heretofore Vpointed out check' pressure in the accumulator 14 forces ball 25 against the valve seat 27, blocking 0E fluid escape.

Advantageously, by using the fluid accumulator 14 as an energy storing device, a given combination of capacity and hoisting speed can be obtained by a lower horsepowery motor than in an ordinary electric hoist. Itshould be noted that the pressure switch 33 turns `on the motor 13 only as required. When idle-the hoist motor is not running, but the hoist is ready to work at the touch ofthe control handle.

Advantageously, the movable jaw 69 is spring loaded so as to open, and the pressure in the fluid chamber 108 closes the jaws. Assuming that the fluid accumulator 14 or the pump 12 or motor 13 fail, the pressure existing in the lower fluid chamber 59 being in communication with the fluid chamber 108, will assure that the jaws 69 and 68 continue to grip the workpiece. The -weight of the load maintains pressure on the fluid trapped in the fluid chamber 59, and this fluid under pressure is lthe supply for the piston 70. Therefore, by properly proportioning the piston 70 and the cylindrical depending piston 54, sufficient clamping force can be provided for any suspended load.

The operating handle 83 is preferably of the illustrated shovel handle type which can be easily gripped for controlling the hoist.

We wish it to be understood that our'invention is not to be limited to the specific constructions and arrangements shown and described, except only in so far as the appended claims may be so limited as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

We claim:

1. In a hoist, the combination of a part adapted to be fixed in a suspended position, a movable part adapted to carry a workpiece, said fixed part having a cylindrical chamber formed therein and said movable part constitut ing a piston movable in said cylindrical chamber, said piston having a relatively large diameter head portion and a downwardly depending shaft portion of reduced diameter so that a relatively large cross section fluid chamber is formed above said piston and a relatively small cross section fluid chamber is formed below saidv large diameter head portion, a source of fluid pressure comprising a motor driven pump and a reservoir connected to said pump, said source of fluid pressure being connected with said small fluid chamber, a valve connected by means of a first conduit with said small fluid chamber and connected by means of a second conduit` able with respect thereto, said valve having a neutral' position in which said first, second and third conduits are blocked and having a rst operative position in which it connects said third conduit with said second conduit and blocks said first conduit and having a second operative position in which it connects said first and second conduits and blocks said third conduit, `and a control handle carried by said movable part and effective on said valve for moving said valve toward its said iirst operative position so as to cause upward movement of said piston when an upward force is put on said handle and for moving said valve toward its said second operative position so as to cause downward movement of said piston when a downward force is put on said handle.

2. In a hoist, the combination of a part that is stationary with respect to vertical movement and adapted to be swingably mounted to a support that is elevated with respect to a working level, a movable part mounted on said part and rotatable with respect thereto, a poweroperated mechanism for raising and lowering said movable part with respect to said part and to move it toward and away from said working level, work piece gripping means carried by said movable part for grasping a work piece when said movable part is moved toward said working level and for raising said work piece when said movable part is moved upwardly, a control handle pivotally mounted on one end thereof on a horizontal axis on said movable part so as to be swingably movable upwardly and downwardly at its other end by a person on said working level, and power control means connected to said control level and effective on said poweroperated mechanism so that when said swingable end of said control handle is moved upwardly said power mechanism is energized to raise said movable part and a work piece carried thereby and when said control handle is moved downwardly said power mechanism is energized to lower said movable part and a work piece carried thereby, said control handle being useable to swing said part and said movable part laterally with respect to said support.

3. In a hoist, the combination of a part that is stationary with respect to vertical movement and adapted to be swingably mounted to a support that is elevated with respect to a working level, a movable part mounted on said part and rotatable with respect thereto, a poweroperated mechanism for raising and lowering said movable part with respect to said part and to move it toward and away from said working level, a movable jaw and a fixed jaw carried by said movable part for grasping a work piece when said movable part is moved toward said ground level and for raising the work piece when the movable part is moved upwardly, a control handle pivotally mounted on one end thereof on a horizontal axis on said movable part so as to be swingably movable upwardly and downwardly at its other end by a person on the working level and useable to swing said part and said movable part laterally with respect to said support, and power control means connected to said control handle and eiective on said power-operated mechanism so that when the swingable end of said control handle is moved upwardly said power mechanism is energized to raise said movable part and a work piece carried thereby and when the control handle is moved downwardly said power mechanism is energized to lower said movable part and a work piece carried thereby, energized power means for holding one of said pair of jaws in proximity to said fixed jaw and a button carried by said handle for de-energizing said power means when depressed and held, and la spring means for causing said movable jaw to move away from said fixed jaw when said button is depressed so as to open said jaws for receiving a work piece and whereupon release of said button the said movable jaw moves toward said fixed jaw to grasp a work piece.

4. In a hoist, the combination of a part that is stationary with respect to vertical movement and adapted to be swingably mounted to a support that is elevated with respect to a working level, a movable part mounted on said part and rotatable with respect thereto, a poweroperated mechanism for raising and lowering said movable part with respect to said part and to move it toward and away from said working level, a moveable jaw and a fixed jaw carried by said movable part for grasping a work piece when said movable part is moved toward said ground level and for raising the work piece when the movable part is moved upwardly, a control handle pivotally mounted on one end thereof on a horizontal axis on said movable part so as to be swingably movable upwardly and downwardly at its other end by a person on the working level and useable to swing said part and said movable part laterally with respect to said support, and power control means connected to said control handle and effective on said power-operated mechanism so that when the swingable end of said control handle is moved upwardly said power mechanism is energized to raise said movable part and a work piece carried thereby and when the control handle is moved downwardly said power mechanism is energized to lower said movable part and a work piece carried thereby, energized power means for holding one of said pair of jaws in proximity to said tixed jaw and a button carried by said handle for de-energizing said power means when depressed and held, a spring means for causing said movable jaw to move away from said fixed jaw when `said button is depressed so as to open said jaws for receiving a work piece and whereupon release of said button the said movable jaw moves toward said fixed jaw to grasp a work piece, and a guard associated with said button to prevent accidental pressure contact against said button.

5. In a hoist, the combination of a part that is stationary with respect to vertical movement and adapted to be swingably mounted to a support that is elevated with respect to a working level, a movable part mounted on said part and rotatable with respect th-ereto, a poweroperated mechanism for raising and lowering said movable part with respect to said part and to move it toward and away from said working level, work piece gripping means carried by said movable part for grasping a work piece when said movable part is moved toward said working level and for moving the work piece upwardly when said movable part is moved away from said working level, a U-shaped control handle pivotally mounted at its open end on a horizontal axis on said movable part so as to be swingably movable upwardly and downwardly at its closed end by a person on the working level, said closed end comprising a horizontally extending bar for grasping by an operator for convenience in lateral movement of said movable part under the influence of pressure exerted laterally by the operator, and power control means connected with respect to said control handle and effective on said power-operated mechanism so that when the swingable end of said control handle is moved upwardly said power mechanism is energized to raise said movable part and a work piece carried thereby and. when the control handle is moved downwardly said power mechanism is energized to lower said movable part and a work piece carried thereby.

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